In recent years, an inkjet method that makes it possible to discharge a liquid at high speed has been utilized in order to supply a drug solution or a reagent, or in order to carry out three-dimensional-shape patterning using cells, in the fields of medicine, drug discovery, and biotechnology.
In the publication of Japanese Patent No. 5,540,304, one single nozzle is used to discharge a solution including cells. However, patterning based on one single nozzle has a problem of poor productivity. In recent years, it has been desired to discharge solutions by use of multiple nozzles, in order to improve productivity.
Furthermore, a solution including particles such as cells easily causes sedimentation of the particles. If sedimentation of particles occurs, and the particles remain at the same location for a long time, the particles adhere to one another, thus forming into large grains, or the solution including particles becomes inhomogeneous.
Therefore, the publication of Japanese Patent No. 5,371,678 has proposed a circulation method in which a solution including particles is circulated to suppress sedimentation of the particles.
In particular, in cases where a solution including particles such as cells is discharged by using an inkjet head, it is required that a solution that comes into a state in which the cells are homogenously dispersed is prepared while sedimentation of particles is suppressed, and that the solution is discharged to homogenize the density of the solution. Furthermore, in case where a solution including cells is discharged from multiple nozzles, it is also required that cell densities are evened among multiple nozzles.